1. Technical Field
The present invention relates to a deployment door assembly for an inflatable vehicle occupant restraint module.
2. Description of the Prior Art
A known vehicle occupant restraint module includes an air bag and a gas source. The air bag is stored in a folded, deployment-ready position inside a housing. The gas source is also typically located in the housing. The housing has a deployment door which has a closed position protecting the air bag and gas source. The deployment door is moved to an open position when the air bag is inflated.
A known deployment door is a single hinged door which extends across an opening in the housing. The hinged door is held in place until the stored air bag begins to inflate. The inflating air bag forces the door to swing open as the air bag deploys through the opening.
Another known deployment door comprises two door flap portions Joined by a tear seam. The tear seam retains the two flap portions together prior to deployment of the air bag. When the air bag begins to inflate, the air bag causes the tear seam to rupture and the two flap portions pivot outward to permit the air bag to deploy.
A door assembly for an air bag module may be exposed to a wide range of temperatures during the life of the vehicle in which the door assembly is mounted. The door assembly should desirably open under the application of the same amount of force from the deploying air bag, regardless of temperature. Door assemblies which use a door with a built-in tear seam are made of plastic materials with properties that tend to change with temperature. As the temperature varies, the amount of force required to open the tear seam may vary.